Measuring devices for detecting operating variables of an internal combustion engine and/or of the motor vehicle are widely used in modern control systems for engines. The measuring signals of the measuring devices form the basis for the control of the engine. Computing elements are also used for carrying out the control function. Unwanted operating conditions of the engine can result because of faults in the area of the measuring devices and/or of the computer elements. For this reason, the necessity is present for monitoring the operation of the measuring devices and/or of the computing elements. Such a check is especially significant for electronic motor power control systems (electronic accelerator pedal systems) wherein the power of the engine and therefore the speed and acceleration of the motor vehicle is controlled on the basis of signals from position transducers of an operator-controlled element and, if required, of a power transducer element by means of at least one computing element. For this reason, various methods for monitoring the position transducer and the computing elements have been suggested in the past. For example, U.S. Pat. No. 4,603,675 discloses that a second position transducer can be provided and a fault measure is initiated when the signal values of the two position transducers deviate from each other by a pregiven tolerance range. Furthermore, for monitoring the control loop or the computer function, the difference between the position of the operator-actuated element and the position of the power actuating element of the engine can be checked for an impermissible deviation. U.S. Pat. No. 4,881,227 discloses that two completely redundant computers can be provided which mutually monitor each other with the aid of the data exchange and with the aid of watchdog signals.
These measures can ensure a comprehensive operational reliability of such a system but lead to increased complexity because of the comprehensive monitoring and, in extreme cases, can lead to fault announcements which are unwanted because they are unnecessary.